Based on the nature of the in-flight engine shutdown (IFSD) and the observations and conclusions of the engine teardown and reports, it was concluded that the IFSD was ultimately caused by fuel starvation due to a loss of drive to theAGB. The AGBdrives the fuel metering unit and integral fuel pump. The No. 29 and No. 30 bearings support the tower shaft in a cavity above the No.3 and No.4 bearing cavity. The loss of drive to the AGB was caused by the failure of the No.30 thrust bearing at the base of the tower shaft. Failure of this bearing allowed the driven spiral bevel gear shaft (tower shaft) to lift longitudinally and disengage from the driving spiral bevel gear on the HPcompressor shaft. Although the balls of the No.30 bearing were damaged to the point that surface material analysis was precluded, corrosion stains and pitting were noted in several places along this power train, including all three bearings (which lie in a vertical orientation). It was concluded that distress occurred to the No.30 bearing as a result of instability due to spalling. The spalling was initiated by corrosion, and the resulting instability produced fatigue fractures in the bearing cage and outer ring, ultimately resulting in disintegration. Records since July 2002 indicate that the aircraft had only flown 104hours in the last 35months and that there were two notable periods of time that it was not in service. Records for those periods indicate that engine idle runs or storage inspections were completed in accordance with the maintenance instructions specified. At some time, a contaminant was introduced into the engine and it is concluded that the most likely opportunity was between February and May2004 when the engine was undergoing repairs. The cover plate of the angle gearbox enclosing the No.29 bearing had been removed and may have been left off and/or re-installed without its preformed packing, allowing contaminant ingress at the cover plate when leaks in the building roof occurred. The contaminant migrated down this power train by gravity from the No.29 bearing through the No.30 bearing and onto the No.4 bearing. The maintenance actions completed were not sufficient to prevent or detect contaminant ingress while the engine was in the shop. The system then remained stationary long enough for corrosion of the bearings along the AGB drive train to occur. Although the TM chip detector recorded a fault due to metal in the engine oil, this warning was not available to the flight crew and, consequently, they had no prior indication of the impending failure and IFSD. The following TSB Engineering Laboratory report was completed: LP 065/2005 - Engine Examination This report is available upon request from the Transportation Safety Board of Canada.Analysis Based on the nature of the in-flight engine shutdown (IFSD) and the observations and conclusions of the engine teardown and reports, it was concluded that the IFSD was ultimately caused by fuel starvation due to a loss of drive to theAGB. The AGBdrives the fuel metering unit and integral fuel pump. The No. 29 and No. 30 bearings support the tower shaft in a cavity above the No.3 and No.4 bearing cavity. The loss of drive to the AGB was caused by the failure of the No.30 thrust bearing at the base of the tower shaft. Failure of this bearing allowed the driven spiral bevel gear shaft (tower shaft) to lift longitudinally and disengage from the driving spiral bevel gear on the HPcompressor shaft. Although the balls of the No.30 bearing were damaged to the point that surface material analysis was precluded, corrosion stains and pitting were noted in several places along this power train, including all three bearings (which lie in a vertical orientation). It was concluded that distress occurred to the No.30 bearing as a result of instability due to spalling. The spalling was initiated by corrosion, and the resulting instability produced fatigue fractures in the bearing cage and outer ring, ultimately resulting in disintegration. Records since July 2002 indicate that the aircraft had only flown 104hours in the last 35months and that there were two notable periods of time that it was not in service. Records for those periods indicate that engine idle runs or storage inspections were completed in accordance with the maintenance instructions specified. At some time, a contaminant was introduced into the engine and it is concluded that the most likely opportunity was between February and May2004 when the engine was undergoing repairs. The cover plate of the angle gearbox enclosing the No.29 bearing had been removed and may have been left off and/or re-installed without its preformed packing, allowing contaminant ingress at the cover plate when leaks in the building roof occurred. The contaminant migrated down this power train by gravity from the No.29 bearing through the No.30 bearing and onto the No.4 bearing. The maintenance actions completed were not sufficient to prevent or detect contaminant ingress while the engine was in the shop. The system then remained stationary long enough for corrosion of the bearings along the AGB drive train to occur. Although the TM chip detector recorded a fault due to metal in the engine oil, this warning was not available to the flight crew and, consequently, they had no prior indication of the impending failure and IFSD. The following TSB Engineering Laboratory report was completed: LP 065/2005 - Engine Examination This report is available upon request from the Transportation Safety Board of Canada. While the engine was undergoing repairs, the cover plate of the angle gearbox enclosing the No.29 bearing had been removed, and it is likely that contamination from a leaking roof entered the engine, allowing corrosion to take place. Distress occurred to the No.30 bearing as a result of instability due to spalling. The spalling was initiated by corrosion and the resulting instability produced fatigue fractures in the bearing cage and outer ring, ultimately resulting in disintegration. The loss of drive to the accessory gearbox (AGB) was caused by the failure of the No.30 thrust bearing at the base of the tower shaft. Failure of this bearing allowed the driven spiral bevel gear shaft (tower shaft) to lift longitudinally and disengage from the driving spiral bevel gear on the high-pressure compressor shaft. The No. 1 engine in-flight shutdown was ultimately caused by fuel starvation due to a loss of drive to the AGB. The AGB drives the fuel metering unit and integral fuel pump.Findings as to Causes and Contributing Factors While the engine was undergoing repairs, the cover plate of the angle gearbox enclosing the No.29 bearing had been removed, and it is likely that contamination from a leaking roof entered the engine, allowing corrosion to take place. Distress occurred to the No.30 bearing as a result of instability due to spalling. The spalling was initiated by corrosion and the resulting instability produced fatigue fractures in the bearing cage and outer ring, ultimately resulting in disintegration. The loss of drive to the accessory gearbox (AGB) was caused by the failure of the No.30 thrust bearing at the base of the tower shaft. Failure of this bearing allowed the driven spiral bevel gear shaft (tower shaft) to lift longitudinally and disengage from the driving spiral bevel gear on the high-pressure compressor shaft. The No. 1 engine in-flight shutdown was ultimately caused by fuel starvation due to a loss of drive to the AGB. The AGB drives the fuel metering unit and integral fuel pump. The engine maintenance actions completed during extended shop repairs were not sufficient to prevent the introduction or detection of a contaminant and resultant corrosion of the bearings along the AGB drive train. Although the turbo machine chip detector recorded a fault due to metal in the engine oil, this warning was not available to the flight crew. Consequently, they had no prior indication of the impending failure and in-flight shutdown.Findings as to Risk The engine maintenance actions completed during extended shop repairs were not sufficient to prevent the introduction or detection of a contaminant and resultant corrosion of the bearings along the AGB drive train. Although the turbo machine chip detector recorded a fault due to metal in the engine oil, this warning was not available to the flight crew. Consequently, they had no prior indication of the impending failure and in-flight shutdown. Information was not recovered from the cockpit voice recorder since it was overwritten while external electrical power was applied to the aircraft following the incident flight. The aircraft had flown only 104hours in the last 35months and there were two notable periods of time that the engine/aircraft were not in service. Records for those periods indicate that engine idle runs or storage inspections were completed in accordance with the maintenance instructions specified.Other Findings Information was not recovered from the cockpit voice recorder since it was overwritten while external electrical power was applied to the aircraft following the incident flight. The aircraft had flown only 104hours in the last 35months and there were two notable periods of time that the engine/aircraft were not in service. Records for those periods indicate that engine idle runs or storage inspections were completed in accordance with the maintenance instructions specified. Safety Action Action Taken Pratt & Whitney Canada engaged a contractor to provide a climate-controlled storage facility for inactive engines.